1. Field of the Invention
The present invention relates to a novel chiral methylhydroxylaminopropanol derivative and its use as an intermediate for preparation of (S)-(−)-3-methylamino-1-(2-thienyl)propan-1-ol.
2. Description of Related Art
3-methylamino-1-(2-thienyl)propan-1-ol, especially its optically active enantiomer (the S form), has been shown to be an important intermediate for preparation of (S)-(+)-N-methyl-3-methyl-3-(1-naphthyloxy)-3-(2-thienyl)propylamine oxalate (Duloxetine®), an antidepressant drug. Various methods have been proposed to prepare (S)-(−)-3-methylamino-1-(2-thienyl)propan-1-ol. For example, Chirality, 12, 26 (2000) discloses a process as shown in the following scheme:

In this example, thiophene is used as the starting material to be acylated by Friedel-Crafts reaction so as to form 3-chloro-1-(2-thienyl)-propanone. Hydride reduction of this propanone forms racemic 3-chloro-1-(2-thienyl)-propan-1-ol. Racemic 3-chloro-1-(2-thienyl)-propan-1-ol is then resolved via enzymatic transesterification to form (S)-(−)-3-chloro-1-(2-thienyl)-propan-1-ol. Subsequently, the resulting chiral chloropropanol is aminated to form (S)-(−)-3-methylamino-1-(2-thienyl)-propan-1-ol with methylamine. In this process, the yield of enzymatic resolution is very low (35%). In addition, large excess, 20 equivalents, of methylamine is required for the amination reaction and the overall yield is low (24%), which renders this process economically less competitive.